Benefix

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Benefix

CLINICAL PHARMACOLOGY

Factor IX is activated by factor VII/tissue factor complex in the extrinsic coagulation pathway as well as by factor XIa in the intrinsic coagulation pathway.
Activated factor IX, in combination with activated factor VIII, activates factor
X. This results ultimately in the conversion of prothrombin to thrombin. Thrombin
then converts fibrinogen to fibrin, and a clot can be formed.

After single intravenous (IV) doses of 50 IU/kg of BeneFIX®, Coagulation
Factor IX (Recombinant), in 37 previously treated adult patients (>15 years),
each given as a 10-minute infusion, the mean increase from pre-infusion level
in circulating factor IX activity was 0.8 ± 0.2 IU/dL per IU/kg infused
(range 0.4 to 1.4 IU/dL per IU/kg) and the mean biologic halflife was 18.8 ±
5.4 hours (range 11 to 36 hours). In the randomized, cross-over pharmacokinetic
study in previously treated patients (PTPs), the in vivo recovery using
BeneFIX® (coagulation factor ix recombinant) was statistically significantly less (28% lower) than the recovery
using a highly purified plasma-derived factor IX product. There was no significant
difference in biological half-life. Structural differences of the BeneFIX® (coagulation factor ix recombinant)
molecule compared with pdFIX were shown to contribute to the lower recovery.
In subsequent evaluations for up to 24 months, the pharmacokinetic parameters
were similar to the initial results.

Clinical Studies

In 4 clinical studies of BeneFIX® (coagulation factor ix recombinant) , a total of 128 subjects 56 previously
treated patients [PTPs], 9 subjects participating only in the surgical study,
and 63 previously untreated patients (PUPs) received more than 28 million IU
administered over a period of up to 64 months. The studies included 121 HIV-negative
and 7 HIV-positive subjects.

Fifty-six PTPs received approximately 20.9 million IU of BeneFIX® (coagulation factor ix recombinant) in two
clinical studies. The median number of exposure days was 83.5. These PTPs who
were treated for bleeding episodes on an on-demand basis or for the prevention
of bleeds were followed over a median interval of 24 months (range 1 to 29 months;
mean 23.4 ± 5.34 months). Fifty-five of these PTPs received a median
of 42.8 IU/kg (range 6.5 to 224.6 IU/kg; mean 46.6 ± 23.5 IU/kg) per
infusion for bleeding episodes. All subjects were evaluable for efficacy. One
subject discontinued the study after one month of treatment due to bleeding
episodes that were difficult to control; he did not have a detectable inhibitor.
The subject's dose had not been adequately titrated. The remaining 55 subjects
were treated successfully. Bleeding episodes that were managed successfully
included hemarthroses and bleeding in soft tissue and muscle. Data concerning
the severity of bleeding episodes were not reported. Eighty-eight percent of
the total infusions administered for bleeding episodes were rated as providing
an "excellent" or "good" response. Eighty-one percent of all bleeding episodes
were managed with a single infusion of BeneFIX® (coagulation factor ix recombinant) . One subject developed a
low titer, transient inhibitor (maximum titer 1.5 BU). This subject had previously
received plasma-derived products without a history of inhibitor development.
He was able to continue treatment with BeneFIX® (coagulation factor ix recombinant) with no anamnestic rise
in inhibitor or anaphylaxis, however, increased frequency of BeneFIX® (coagulation factor ix recombinant) administration
was required; subsequently the subject's factor IX inhibitor and its effect
on the half-life of BeneFIX® (coagulation factor ix recombinant) resolved.

Forty-one of the subjects had measurements of fibrinopeptide A and prothrombin
fragment 1 + 2 prior to infusion, 4 to 8 hours and then 24 hours following the
infusion. Twenty-nine of the subjects had elevations in fibrinopeptide A with
a maximum value of 35.3 nmol/L (22 of the 29 subjects had elevated baseline
values). Ten of the subjects had elevated prothrombin fragment 1 + 2 with a
maximum value of 1.82 nmol/L (3 of the 10 subjects had elevated baseline values).

A total of 20 PTPs were treated with BeneFIX® (coagulation factor ix recombinant) for secondary prophylaxis
(the regular administration of FIX replacement therapy to prevent bleeding in
patients who may have already demonstrated clinical evidence of hemophilic arthropathy
or joint disease) at some regular interval during the study with a mean of 2.0
infusions per week. Nineteen subjects were administered BeneFIX® (coagulation factor ix recombinant) for routine
secondary prophylaxis (at least twice weekly) for a total of 345 patient-months
with a median follow-up period of 24 months per subject. The average dose used
by these 19 subjects was 40.3 IU/kg, ranging from 13 to 78 IU/kg. One additional
subject was treated weekly, using an average dose of 33.3 IU/kg, over a period
of 21 months. Ninetythree percent of the responses were rated as "excellent"
or "effective". These 20 PTPs received a total of 2985 infusions of BeneFIX® (coagulation factor ix recombinant)
for routine prophylaxis. Seven of these PTPs experienced a total of 26 spontaneous
bleeding episodes within 48 hours after an infusion.

Total BeneFIX® (coagulation factor ix recombinant) coverage during the surgical period for the major procedures
ranged from 4230 to 385,800 IU. The pre-operative dose for the major procedures
ranged from 75 to 155 IU/kg. Nine of the major surgical procedures were performed
in 8 subjects using a continuous infusion regimen. Following pre-operative bolus
doses (94.1 -144.5 IU/kg), continuous infusion of BeneFIX® (coagulation factor ix recombinant) was administered
at a median rate of 6.7 IU/kg/hr (range of average rates: 4.3-8.6 IU/kg/hr;
mean 6.4 ± 1.5 IU/kg/hr) for a median duration of 5 days (range 1-11
days; mean 4.9 ± 3.1). Six of the 8 subjects who had received continuous
infusion of BeneFIX® (coagulation factor ix recombinant) in conjunction with major surgeries were switched over
to intermittent pulse regimens at a median dose of 56.3 IU/kg (range 33.6-89.1
IU/kg; mean 57.8 ± 18.1 IU/kg SD) for a median of 3.5 exposure days (range
1-5 days, mean 3.3 ± 1.4 SD) during the post-operative period. Although
circulating factor IX levels targeted to restore and maintain hemostasis were
achieved with both pulse replacement and continuous infusion regimens, clinical
trial experience with continuous infusion of BeneFIX® (coagulation factor ix recombinant) for surgical prophylaxis
in hemophilia B has been too limited to establish the safety and clinical efficacy
of administration of the product by continuous infusion. Subjects administered
BeneFIX® (coagulation factor ix recombinant) by continuous infusion for surgical prophylaxis also received intermittent
bolus infusions of the product.

Hemostasis was maintained throughout the surgical period, however, one subject
required evacuation of a surgical wound site hematoma and another subject who
received BeneFIX® (coagulation factor ix recombinant) after a tooth extraction required further surgical intervention
due to oozing at the extraction site. There was no clinical evidence of thrombotic
complications in any of the subjects. In seven subjects for whom fibrinopeptide
A and prothrombin fragment 1 + 2 were measured pre-infusion, at 4 to 8 hours,
and then daily up to 96 hours, there was no evidence of significant increase
in coagulation activation. Data from two other subjects were judged to be not
evaluable.

Sixty-three PUPs received approximately 6.2 million IU of BeneFIX® (coagulation factor ix recombinant) in an
open-label safety and efficacy study over 89 median exposure days. These PUPs
were followed over a median interval of 37 months (range 4 to 64 months; mean
38.1 ± 16.4 months). Fifty-four of these PUPs received a median dose
of 62.7 IU/kg (range 8.2 to 292.0 IU/kg; mean 75.6 ± 42.5 IU/kg) per
infusion for bleeding episodes. Data concerning the severity of bleeding episodes
were not reported. Seventy-five percent of all bleeding episodes were managed
with a single infusion of BeneFIX® (coagulation factor ix recombinant) . Three of these 54 subjects were not
successfully treated; including one episode in a subject due to delayed time
to infusion and insufficient dosing and in 2 subjects due to inhibitor formation.
One subject developed a high titer inhibitor (maximum titer 42 BU) on exposure
day 7. A second subject developed a high titer inhibitor (maximum titer 18 BU)
after 15 exposure days. Both subjects experienced allergic manifestations in
temporal association with their inhibitor development.

Thirty-two PUPs administered BeneFIX® (coagulation factor ix recombinant) for routine prophylaxis. Twenty-four
PUPs administered BeneFIX® (coagulation factor ix recombinant) at least twice weekly for a total of 2587 infusions.
The mean dose per infusion was 72.5 ± 37.1 IU/kg, and the mean duration
of prophylaxis was 13.4 ± 8.2 months. Eight PUPs administered BeneFIX® (coagulation factor ix recombinant)
once weekly for a total of 571 infusions. The mean dose per infusion was 75.9
± 17.9 IU/kg, and the mean duration of prophylaxis was 17.6 ±
7.4 months. Five PUPs experienced a total of 6 spontaneous bleeding episodes
within 48 hours after an infusion.

Twenty-three PUPs received BeneFIX® (coagulation factor ix recombinant) for surgical prophylaxis in 30 surgical
procedures. All surgical procedures were minor except 2 hernia repairs. The
preoperative bolus dose ranged from 32.3 IU/kg to 247.2 IU/kg. The perioperative
total dose ranged from 385 to 23280 IU. Five of the surgical procedures were
performed using a continuous infusion regimen over 3 to 5 days. Clinical trial
experience with continuous infusion of BeneFIX® (coagulation factor ix recombinant) for surgical prophylaxis
in hemophilia B has been too limited to establish the safety and clinical efficacy
of administration of the product by continuous infusion.

Last reviewed on RxList: 9/18/2008
This monograph has been modified to include the generic and brand name in many instances.